Cyber Resilience

CVE-2026-59564

Auth Bypass

Auth Bypass
Published
24 August 2026
Modified
12 October 2026
CVSS Score v3.1 9.1
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
EPSS Score 0.0053 43th percentile
Risk Priority 67 floored blend · peak EPSS

CVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.

Summary

CVE-2026-59564 is a critical-severity Missing Critical Step in Authentication (CWE-304) vulnerability in Zscaler Client Connector (inferred from references). Its CVSS base score is 9.1 (Critical).

Operationally, ranked at the 43th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to IA-2 (Identification and Authentication (Organizational Users)) and IA-5 (Authenticator Management) — see the control section below for these in your framework.

OWASP Top 10 for Web (2025)

A07:2025 Authentication Failures

EU & UK References

Vulnerability Data

An authentication bypass issue exists in communications between affected versions of the Zscaler Client Connector and the Zscaler Client Connector Portal.

CWE(s)
CWE-304

Related Threats

CVEs Like This One

CVE-2026-76207Shared CWE-304
CVE-2025-55138Shared CWE-304
CVE-2024-45764Shared CWE-304
CVE-2024-52965Shared CWE-304
CVE-2024-20153Shared CWE-304
CVE-2025-24322Shared CWE-304
CVE-2026-55957Shared CWE-304
CVE-2023-54391Shared CWE-304
CVE-2026-42452Shared CWE-304
CVE-2025-43014Shared CWE-304

Affected Assets

Zscaler
Client Connector
inferred from references and description; NVD did not file a CPE for this CVE

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)
  • 6 hardening rules · 2 OS baselines
Validate
Prove the fix (OWASP ASVS)
  • V7.2.4

Mitigating Controls (NIST 800-53 r5) AI

IA-2 Identification and Authentication (Organizational Users) good match

IA-2 requires unique identification and authentication of users, directly mandating that all critical authentication steps be performed rather than skipped.

IA-8 Identification and Authentication (Non-organizational Users) good match

IA-8 requires unique identification and authentication of non-organizational users, ensuring the full authentication process is executed without missing steps.

IA-5 Authenticator Management good match

IA-5 enforces proper authenticator lifecycle steps (verification, distribution, revocation) so that no required step in the authentication technique is omitted.

AC-3 Access Enforcement partial match

AC-3 enforces access decisions only after approved authentication has completed, making skipped authentication steps ineffective.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.AA-02 partial match
blocks

Proper identity proofing and credential binding prevents skipping enrollment steps that weaken authentication.

PR.AA-03 partial match
blocks

Requiring complete authentication (e.g., MFA, password policy) directly stops omission of critical steps in the auth process.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.5.14 Information transfer partial match
removes
A.5.15 Access control partial match
removes
A.5.16 Identity management partial match
removes
A.5.17 Authentication information partial match
removes
A.5.18 Access rights partial match
removes
A.8.10 Information deletion partial match
removes

Hardening callouts derived

Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (higher-evidence rows only; rows rated `none` are excluded).

RHEL 7 (2 rules)
  • V-204425 The Red Hat Enterprise Linux operating system must be configured so that the SSH daemon does not allow authentication using an empty password. blocks CWE-304
  • V-204424 The Red Hat Enterprise Linux operating system must not allow accounts configured with blank or null passwords. blocks CWE-304
Ubuntu 22.04 (1 rule)
  • V-260470 Ubuntu 22.04 LTS, when booted, must require authentication upon booting into single-user and maintenance modes. blocks CWE-304

References